This invention relates to a system for dispensing to and withdrawing a fluid medium from a balloon catheter for dilatation purposes.
This invention also relates to a stent expansion system comprising a balloon catheter with a tubular shaft having proximal and distal portions, a dilatation balloon mounted on the distal portion of the shaft for expanding an expandable stent, a fluid supply lumen extending throughout the shaft for balloon inflation, and a pressure source for dispensing to and withdrawing a fluid medium from the balloon via the supply lumen.
The invention further relates to a machine for pulsating the medium inflating the balloon of a catheter arrangement having a shaft, a dilatation balloon mounted on the shaft, a fluid supply lumen extending throughout the shaft for balloon inflation, and a pressure source for dispensing to and withdrawing a fluid medium from the balloon via the lumen.
The invention still further relates to a balloon catheter with a tubular shaft having proximal and distal portions, a dilatation balloon mounted on the distal portion of the shaft, and a fluid supply lumen extending throughout the shaft for balloon inflation.
Balloon catheters are quite currently used for dilating vessels or other body cavities. To this end, the balloon is positioned at the area to be dilated and then fed with a fluid medium to achieve dilatation and thereby expand the vessel. During the treatment, the vessel is occluded by the balloon and the blood supply to the upstream organs is interrupted. A further problem is that some occlusions cannot be dilated because the vessel has achieved a rigidity resisting the dilating pressure executed by the balloon.
U.S. Pat. No. 4,439,186 describes a dilatation catheter with an expandable balloon in communication with an inflation lumen extending along the length of the catheter. The balloon has a pressure-volume relationship which is not linear, and a pressure source is provided which supplies a pulsating pressure to the balloon for alternating expansion and contraction thereof. The source of fluctuating pressure comprises a pump supplying a fluid to a container filled with the fluid and which is provided with a flexible bottom connected to the magnetic core of an electromagnet. The container is connected to the dilatation balloon and energizing of the electromagnet causes the magnetic core to move the flexible bottom of the container, thus producing a corresponding pressure pulse or a series of pressure pulses in the fluid within the container. By alternating expansion and contraction of the balloon the blood may circulate during the periods of time during which the vessel is not under action of the balloon. Connection of the container of pressure fluid to the core of an electromagnet requires serious insulation measures in order to avoid any risk of having the patient or other attendant materials in contact with electric current.
U.S. Pat. No. 5,152,776 shows a dilatation balloon catheter fed by a pump controlled by a drive mechanism. The actual fluid conditions present in the balloon are identified by a monitor and communicated to a microprocessor sending orders to the drive mechanism in accordance with a predetermined pattern in order to prevent prolonged cessation of blood flow to sites distal from the action. This structure does not allow the feed of any pulsating pressure to the balloon.
U.S. Pat. No. 4,446,867 shows a fluid driven balloon catheter comprising a catheter with a through going lumen, a fluid supply inflation device attached to one end of the catheter, and a balloon attached to the other end. A pulse generator is provided for generating pressure pulses in the fluid through the lumen to sharply expand and contract the balloon at intervals. This pulse generator comprises a pulse inflation device communicating with the catheter lumen via a T joint and valve, a spring driven ram to bump upon the piston of the pulse inflation device, and a cam rotor to move the ram away from the piston of the pulse inflation device, whereby when the cam moves the ram away from the piston of the pulse inflation device, the spring of the ram is compressed until the cam rotates further and releases the ram to strike the piston of the pulse inflation device. By this pulse action, it is said that the occlusive material in the vessel, which is more brittle than the surrounding vessel wall will crack. However, the friction of the piston in the pulse inflation device of the pulse generator will substantially damp down the pulse action. Furthermore, the hammer operation of the spring loaded ram may cause non negligible stresses on both the piston and pulse inflation device.
The balloon catheter is also an instrument of common use as a mechanism for transporting and applying by expansion a balloon expandable prosthesis, called a stent, for maintaining the patency of a vessel. It is also used for completing the expansion of self-expandable stents which are not transported and applied by a balloon catheter but by a specially devised hollow catheter.
Expansion of a stent requires however a relatively high pressure in the balloon, at least for the last stage force needed to seat or press the stent against the vessel wall. High balloon pressures may induce the risk of overpressure causing trauma to the vessel wall; they also induce the risk of bursting the balloon and further wounding the patient. Furthermore, it is difficult to modulate the pressure in the balloon to precisely control the stent expansion and its embedding into the vessel wall. These difficult conditions need a lot of attention for the expansion manipulation, which is an added load for the practitioner.
There is no suggestion in the documents referred to hereinabove that pulsation of the fluid medium feeding a balloon catheter could be envisaged as a help for stent expansion. Moreover, it has always been considered that a sharp highblow is the way to properly expand and seat a stent in the vessel wall.
It is an object of this invention to propose a fluid delivery for a balloon catheter and a stent expansion system which are highly versatile, simple to manufacture, and easy to use. A further object of the invention is to propose a machine for pulsating the fluid medium inflating the balloon of a balloon catheter arrangement which is highly versatile and very easy to operate, which is simple to manufacture, and which affords a high degree of safety for the patient. Still a further object of the invention is a balloon catheter particularly adapted for a versatile usage.